420CL钢轮辋焊缝开裂分析

Analysis onWeld Cracking of 420CLSteel Wheel Rim

通过光学显微镜、扫描电镜、能谱仪检测等手段,对420CL钢制轮辋开裂焊缝进行断口分析,确定导致焊缝开裂的原因。结果表明:轮辋焊缝裂纹开裂方式为解理断裂,裂纹源附近焊缝中存在大量Mn、Si等元素的氧化物夹杂。夹杂物的存在导致焊缝组织处金属基体组织连续性变差,造成焊缝塑性降低,是焊缝在扩形时开裂的根本原因。焊缝中氧化物夹杂的产生,是由于闪光对焊时,未完全熔化的MnO_(2)和SiO_(2)氧化物在顶锻时未被挤出,从而残留在焊缝内形成夹杂物。建议通过提高闪光焊边部的停留时间、加大顶锻行程来减少焊缝端部氧化物夹杂的存在,从而降低焊缝开裂率。

By optical microscope,scanning electron microscope,energy spectrometer and other means,the fracture analysis of the cracked weld of 420CL steel rim was carried out to deter find mine the cause of weld cracking.The results show that the cracking mode of the rim weld is cleavage fracture,and there are a lot of oxide inclusions of Mn,Si and other elements in the weld near the crack source.The existence of inclusions leads to the deterioration of the continuity of the metal matrix structure at the weld structure,resulting in the reduction of the weld plasticity,which is the root cause of the cracking of the weld during expansion.The occurrence of oxide inclusions in the weld is due to the fact that the incompletely melted MnO_(2) and SiO_(2) oxides are not extruded during upsetting during flash butt welding,so they remain in the weld to form inclusions.It is suggested to reduce the presence of oxide inclusions at the end of the weld by increasing the residence time of the flash welding edge and increasing the upsetting stroke,thereby reducing the cracking rate of the weld.